Is there one best way of doing therapy?

I believe that over time, hypnotherapists tend to get stuck in whatever approach they were trained in. Some hypnotherapists use mostly regression. Others tend to focus on Direct Suggestion. I personally favor Metaphor approaches. However every therapist should be continually expanding their toolbox of techniques.

It is always a mistake to decide too quickly what the problem is, and then apply your standard tool. The basic problem is that humans tend to see what they expect see. We  ignore any evidence that does not fit our initial assumptions. Deliberately using one of more models of therapy will help to avoid that.  There is one well known model that you should use, or at least, consider when assessing clients.

Multi Modal Therapy

This therapy model sees people as having multiple ways of experiencing the world, and of reacting to their world.  The BASIC ID model asks you to consider each of seven modalities before deciding your approach.

B represents behavior, indicated by inappropriate acts, habits, gestures, or the lack of appropriate behaviors.
A stands for affect, which is shown by the level of negative feelings or emotions the client talks about.
S is sensation, or the negative bodily sensations or physiological symptoms such as pain, tension, sweat, nausea, quick heartbeat, etc.
I stands for imagery, evidenced by negative cognitive images or mental pictures.
C represents cognition or the degree of negative thoughts, attitudes, or beliefs.
The second I stands for interpersonal relationships, and refers to your ability to form successful relationships with others. It is all about missing social skills and support systems.
D is for drugs and biological functions, and examines the individual's physical health, drug use, and other lifestyle choices.

(Source: Wikipedia)

How to use Multi Modal Therapy

You listen to the client and as you interact, you note any words or behavior that indicates they are using one or more modalities. Each person will have a mix of modalities. Some people will be mostly cognitive. But they may be hypervigilant, or have negative thinking as well. Some people will be mostly visualizers, daydreaming or catastrophizing future outcomes, but also feel things strongly in their body.

When you establish what their dominant modality is, then you can discuss how to make the changes the client wants. A visualizer could be introduced to NLP therapies, or EMDR. A cognitive person might be offered CBT. A person whose problems are really lifestyle problems might be offered mainly counselling. Each modality suggests its own response.

Applying this model can help you avoid over-narrow thinking, and leave open to learning other psychological techniques.